Natural gas is collected in gas wells which intersect with gas-bearing formations. If water in a gas well rises to a level above a gas-bearing formation or collects in a tubing or casing, then the water can interfere with the efficient collection of natural gas. It is therefore necessary to provide a means to remove water from the well.
In the production of coal bed methane, it is necessary to pump water from a well in order to decrease the head of water in a coal seam to just below the top of the seam. Removal of water releases the pressure holding the gas in the coal seam. This frees the gas so that it can be extracted.
Pump jacks are often used to remove water from gas wells. A pump jack is a device located at the surface which reciprocates a pump rod by rotation of a crank driven by a motor. The motor rotates a counter-weighted crank, thereby causing a beam to move up and down. The beam drives a pump rod, which extends to a pump located in the well bore at or above or below the gas bearing formation, thereby operating the pump. Although common, pump jacks are bulky and expensive to use. Additionally, they are prone to gas lock during operation.
Soberg, Canadian patent No. 466,781 discloses a deep well pump. A pump cylinder contains a hollow piston adapted to be reciprocated by variation of the static pressure of a liquid column above the piston. Downward movement of the hollow piston is provided by an increase in pressure above the liquid. This drives liquid into the hollow piston, compressing a body of gas. The pressure on the liquid above the piston is then decreased. The piston then rises under the influence of a suitable spring or metal bellows positioned beneath the cylinder. This pump requires an air chamber within the cylinder, which limits the liquid-pumping capacity of the pump.
Canalizo, Canadian patent No. 1,203,749 discloses a second design for a deep well pump. This pump uses a power piston and a production piston that are rigidly interconnected. A hydraulic fluid acting on the power piston moves the power piston downward, causing a production cylinder to fill with fluid. When the hydraulic force on the power piston fluid is removed, both pistons are moved in the opposite direction, either by using a power fluid of lesser density than the production fluid, or by isolating the hydrostatic head of fluid in the tubing from the production cylinder so that the production cylinder is subjected to bottom hole pressure that is less than the tubing pressure at the pump.
There remains a need for reliable and cost effective apparatus and methods for pumping in deep wells.